1. Field of the Invention
The present invention relates to a data transmission unit. More specifically, it relates to a data transmission unit for transmitting data sent in over a plurality of transmission paths at random time intervals to a single transmission path through autonomously arbitration.
2. Description of the Related Art
In processing equipment such as an electronic computer, a plurality of processing units are communicatively coupled by digital signals, to perform data processing In general, contents of data processed in a distributed manner are varied with the processing units, while data required for such processing and results obtained in the respective processing units are different from each other. When interconnection is performed for each data processing required for data transfer with an input/output port in order to couple such a plurality of processing units, the hardware for the equipment is extremely complicated and the size and cost of the entire apparatus is increased.
The inventors have proposed a data transmission unit for transmitting different types of data groups through the same data transmission path as disclosed in Japanese Patent Laying-Open Gazette No. 174857/1987.
FIG. 1 is a block diagram schematically showing illustrating the data transmission unit proposed by the inventors.
Referring to FIG. 1, a brief description is now made for the data transmission unit, which branches data to two transmission paths for transmitting data. Each of the data transmission paths 1, 7 and 8 in FIG. 1 is formed by a data register for transmitting data and a transfer control part. An identifier transmission path 2 is provided in parallel with the data transmission path 1. The identifier transmission path 2 is adapted to transmit an identifier called a tag. This identifier indicates whether the data received on the data transmission path 1 is to be transmitted to the data transmission path 7 or the other path 8.
When both of the data transmission paths 7 and 8 are empty for enabling data transmission subsequent data transmission paths (not shown) supply UK signals 5a and 6a to control parts 5 and 6 respectively. Similarly, UL signals 5d and 6d from preceding stages of the data transmission paths 7 and 8 are also supplied to the control parts 5 and 6 respectively. The UL signals 5d and 6d are supplied from arbitrary data transmission paths which precede the data transmission paths 7 and 8, for indicating that the data transmission paths 7 and 8 are empty for enabling data transmission. Upon inputting the UK signal 5a, the UL signal 5d, the UK signal 6a and the UL signal 6d, the control parts 5 and 6 determine that the data transmission path 7, the preceding the path, the data transmission path 8 and the preceding path are empty respectively, for transmitting data, which may be theretofore held, to subsequent stages, and active states for enabling branch control of subsequent input data may be entered.
A NOR gate 4 receives the signals 56 and 66 from the control parts 5 and 6 indicating that the control parts are empty and activated, for supplying an AK signal to the data transmission path 1 and the identifier transmission path 2. Thus, data transmission from the control parts 5 and 6 to the data transmission paths 7 and 8 is permitted or inhibited while branching/transmission of data from the data transmission path 1 to the control part 5 and 6 is permitted or inhibited by the UK and UL signals from the data transmission paths 7 and 8 and the preceding same, depending on whether or not the preceding transmission paths are empty.
The identifier transmission path 2 supplies an identifier decoding part 3 with an identifier, which shows that the data received on the data transmission path 1 is to be transmitted to the data transmission path 7, for example. The identifier decoding part 3 decodes the identifier received from the identifier transmission path 2 and supplies a control signal 5c to the control part 5 for activating the control part 5. Thus, the data received from the data transmission path 1 can be transmitted to the data transmission path 7 through the control part 5. On the other hand, when the identifier transmission path 2 supplies the decoding part 3 with an identifier indicating that the data is to be transmitted to the data transmission path 8, the identifier decoding part 3 supplies a control signal 6c to the control part 6 for activating the control part 6. Thus, the data received on the data transmission path 1 can be transmitted to the data transmission path 8 through the control part 6.
Within the data transmission paths 7 and 8 and the preceding paths, when the data transmission path 7 currently holds or transmits data, for example, no UK signal 5a is supplied to the control part 5. Also, when the transmission path preceding the data transmission path 7 currently holds or transmits data, no UL signal 5d is supplied to the control part 5. Thus, the control part 5 determines that the data transmission path 7 or the preceding path is currently in transmission or in a busy condition, for storing data inputted in a register (not shown) included in a control part 10 while supplying a high-level signal to one input terminal cf the NOR gate 4. Thus, the NOR gate 4 is closed so that nc AK signal is supplied to the data transmission path 1 and the identifier transmission path 2.
In other words, when any of the data transmission paths 7 and 8 and the preceding paths currently hold or transmit data while the control parts 5 and 6 hold data, data received on the data transmission path 1 is not inputted in the control parts 5 and 6 but data is held in the data transmission path 1. When the data transmission path 7, the preceding path, the data transmission path 8 or the preceding path completes data transmission to cause a transition from a busy condition to an empty state, the control part 5 or 6 is activated. Thus, the data held in the data transmission path 1 can be autonomously branched again in accordance with the identifier.
In the aforementioned data transmission unit, the time required for processing distributed data is varied with the received data and the processing contents required for the unit, while data groups are not necessarily transmitted regularly in the same order at the same time intervals, as a result of the processing. If the transmission paths themselves can be provided with a buffer function for minimizing quantities of transmission data groups held up due to dispersion in the processing, hardware of the processing unit can be reduced.